Every once in a while, my Arduino IDE suddenly takes forever to launch, sticking at the splash screen for a long time. Even after it launches, it’s still basically unusable, because the pull-down menus also freeze up, and take an eternity to respond. It happens to me every time I download a new Arduino IDE, which is so infrequent that repeatedly forget why it happens, and how to fix it. After ripping my hair out for a while, I start googling until I find the fix.
If you’re experiencing this problem running Arduino on Microsoft Windows, chances are, you have a virtual serial port from a Bluetooth SPP device installed in your system. The problem is that the Arduino IDE is trying to enumerate your system’s serial ports in order to locate the attached Arduino devices, and the code takes a long time to timeout. Luckily, user eried in the Arduino forums figured out what was happening, and posted a fix in the thread: Road to solve the delay in Arduino IDE. He has graciously come up with a workaround, and shared it with us.
The fix is easy. Simply download his rar file, extract his new rxtxSerial.dll, and replace the version that’s currently in the same directory where your arduino.exe resides. I’ve also attached a zip archive of the file below, for those people who don’t want to install WinRAR in order to get the new rxtxSerial.dll. Thanks, eried!